Propeller type turbines that have a number of blades extending radially from a central hub are well known. Incident wind causes the propeller blades to rotate about the hub, causing a shaft to rotate within a generator to generate electricity.
The problem with known turbine arrangements is that they rely upon large structures and heavy non flexible blade designs, which reduces efficiency and makes them very difficult to erect and maintain. It is also necessary to angle the blades into the direction of oncoming wind, which requires the nacelle of the turbine to be pivotable about the main support. Again, this makes for a more complicated design with more moving parts.
Also known in the art are vertical axis wind turbines such as the Darrieus design. Darrieus turbines have a number of aerofoils, typically two, mounted vertically about a rotating shaft. In constant wind speeds the Darrieus type turbine can, in theory, operate as efficiently as the propeller type turbines, but in practice physical stresses, design limitations and wind speed variation result in them being less efficient. Darrieus turbines can also be difficult to erect and often require complex support tethers or frames, as well as being vulnerable to high wind conditions.
We have appreciated that there is a need to provide a turbine generator that can be easily erected, and that has lightweight blade structure, whilst still retaining a strong structure and being able to control the speed at which the turbine rotates in all wind conditions.